Memories of the 1989 Loma Prieta Earthquake

Abstract

The 17 October 1989 M 6.9 Loma Prieta earthquake was the most significant earthquake to impact the San Francisco Bay region since 1906. It occurred 26 min before the scheduled start of the third game of the World Series between the San Francisco Giants and their across-the-bay rivals, the Oakland A’s. Those watching the pregame TV broadcasts from north of San Francisco saw the impacts of the strong shaking at Candlestick Park well before the shaking hit them—a clear demonstration of the physics underlying earthquake early warning systems: electromagnetic transmission is about 100,000 times faster than the propagation of seismic waves through the earth. Every earthquake is different, with unique features, and the Loma Prieta earthquake was unique in many respects. This article describes some of those unique aspects from the perspective of the Seismology Branch of the U.S. Geological Survey, located in Menlo Park, California, roughly midway between the epicenter and Candlestick Park.